1. Field of the Invention
The present invention relates to a method for measuring axial deviation in a taut wire alignment system. It also relates to a measuring device implementing this method and a taut wire alignment system including such measuring devices.
2. Description of the Related Art
In large instruments used in particle physics research, such as linear colliders, it is necessary to obtain a precise alignment of heavy elements such as magnet sections, over distances which can be as great as several hundred meters. For this purpose, there have been developed non-contact alignment systems making use of a wire stretched along the length of the elements to be aligned and devices for measuring deviation using optical or electrical techniques, in particular capacitive techniques. The present invention falls within the category of taut wire alignment systems using capacitive measuring techniques. In this context, a taut wire alignment system is already known in which there is sent along an electrically conductive wire a short pulse with a time constant of one nanosecond. This pulse induces electrostatic charges between two metal plates by influence. A measurement of charge difference provides quantitative information on the deviation of the wire with respect to the median plane between the two plates.
Another taut wire alignment system is known in which a tungsten wire of diameter 125 .mu.m and having a resistivity of 40 .OMEGA.m is subjected to a high frequency alternating voltage. Capacitive pick-up rings are disposed between guard segments connected to earth. These rings and the electronics are disposed in a screened case.
In these alignment systems, the conductivity of the taut wire is used for making measurements of the axial deviation, which excludes the use of materials having high electrical resistivity for making these wires.